1. Field of Invention
This invention relates to new and improved methods of protecting the environment from oil spills in electric power distribution and generating facilities, and the separation of oil from water by automatic means using newer technology for detecting oil/water interface.
2. Description of Prior Art
Electric power distribution substations are located in or near every populated area. Many of these substations are located near streams or other bodies of water. They can also be located near underground water supplies which are tapped by water wells for household or other consumption.
The problem lies in that the electrical devices located in these substations (transformers, circuit breakers, load tap changers and regulators) contain dielectric insulating oils in large quantities. Many of these oils also contain PCB's, which are a major health hazard. These devices are subject to conditions under which the oil contained in them may be leaked into the surrounding environment. Overheating or lightning strikes can cause fires and subsequent rupture of the oil containing vessel spilling hundreds or thousands of gallons of oil. Vandalism with the use of firearms also may result in spills with projectiles penetrating the vessel walls. Oil drain valves on the vessels themselves can also leak or be accidentally left open.
Some power companies have built concrete containment basins around the oil containing equipment in some of their substations in an effort to contain spills. There is still a problem however, because the basins can fill up with rainwater leaving too little room for the volume of oil that could be spilled. A spill occurring with water in the basin, or a heavy rainfall after a spill would result in oil overflowing the walls of the containment basin. Some companies included a manually operated drain valve by which the basin could be emptied of water, but this requires constant checking by company personnel. This is not feasible due to the large number of these substations and their sometimes remote locations. In this age of corporate downsizing and reduced numbers of personnel, many of these substations are electronically operated from remote centralized control facilities and are rarely visited for inspection. The manual water drain valve is also subject to accidentally being left open, allowing not only water but any oil present to escape. In addition, the operating company has no way of knowing that a spill has occurred unless an inspection is made or equipment going out of order alerts them to a problem.
Many of these same problems exist at the electric power generating facilities themselves, and sometimes to a greater extent. These facilities ( hydroelectric generating plants, coal and oil fired power plants, nuclear power plants and gas turbine electric generating plants) are by their nature located on or adjacent to bodies of water. They contain the same electrical devices mentioned above except larger and containing more oil. They also have many other sources of potential spills such as reservoirs of turbine generator lubricating oil, hydraulic oil, and in the case of gas turbine generating plants, tanks containing one million or more gallons of diesel fuel oil.
Prior art has described methods of dealing with these problems at the electric generating plants using capacitance sensors to detect an oil/water interface and thereby automatically drain water or water and oil into a collection sump by opening a solenoid valve in the basin. The water or water and oil is then pumped or drained by gravity into a second sump which collects liquids from the entire facility. There a system of float switches and a capacitance sensor attempt to keep water pumped out of the sump and into the adjacent body of water while stopping short of pumping any oil into the same. This system is more completely described in U.S. Pat. No. 5,305,779 to Izaguirre, Apr. 26, 1994. Other methods of separating oil and water are also described in other art which will be disclosed along with the aforementioned patent as a part of this application process. No prior art was found to make claims on an automatic system for releasing water but retaining oil in the containment basin around the electrical devices themselves and no reference is made to distribution substations remote from the power generating facility.
The prior art uses interconnecting piping, valves and pumps to collect water and spilled oil from several sources into a holding sump and then a second collection sump. Pumps are rotating devices which are subject to wear and electrical failure. If a pump fails due to wear, breakage or corrosion, or if the situation which causes the oil spill also knocks out electrical power to the pumps, the system can fail and overflow oil into the surrounding environment. Solenoid valves used in the past have small orifices and tortuous paths within them which are subject to clogging with debris causing malfunction of the drainage system and overflow of oil.
Existing systems require multiple sensors for detecting oil/water interface and controlling water discharge while retaining oil. They also require AC electrical power which may be lost when one of the aforementioned events occur which cause a spill. Other systems have not addressed the need for a means of alarming when a spill occurs at a substation at the generating plant or at a remote location. The existing inventions do not address the possibility of oil entering the containment basin first, filling the water drain pipe with oil which is then released when water enters the basin and automatic controls open the water drain valve. Other methods of separating oil from water require heat which is expensive, or rely on predicted amounts of water to be drained over a period of time which could change. Although other separation methods use electrical sensors they require the use of extraneous electronic logic computation systems. Perhaps of greatest importance is the fact that newer, simpler and less expensive devices for detecting and controlling oil/water interface are now in existence.